Cytoplasmic RNA oxidation is a prominent feature of vulnerable neurons in the brains of Alzheimer's disease (AD) patients. However, the role of RNA oxidation in the pathogenesis of AD is still unknown. We have recently developed a novel procedure to isolate and characterize oxidized RNA. We found that up to 50% of poly(A)+ mRNAs are oxidized in AD brains. Identification of oxidized mRNA species revealed that some mRNAs are more susceptible to oxidative damage; thus, RNA oxidation is not random but highly selective. Importantly, many identified oxidized mRNA species have been implicated in the pathogenesis of AD. Investigation of the consequence of oxidatively damaged mRNAs revealed that oxidized mRNA could not be translated properly leading to reduced protein expression and consequently, loss of normal protein function. Significantly, microinjection of oxidized mRNAs into neuronal cells leads to cell death, suggesting that increased RNA oxidation could lead to cell death. Furthermore, several lines of evidence suggest that RNA oxidation is an early event preceding cell death, not an artifact of dying cells. Taken these studies together, RNA oxidation itself is directly associated with neuronal deterioration instead of harmless epiphenomenona during the process of neurodegeneration. This is an important, yet understudied area. Further detailed investigation is needed. We hypothesize that oxidative damage to mRNA could result in protein malfunction, which could contribute to neuronal death in AD. In Aim 1, we propose to further identify oxidized mRNA species by cDNA microarray, to quantify the oxidation level for each oxidized mRNAs, and to investigate the proteins corresponding to the identified oxidized mRNA species in AD. This study will identify those highly oxidized mRNA species and determine whether proteins corresponding to those highly oxidized mRNA species are defective. In Aim 2, we propose to investigate the biological consequence of RNA oxidation. These studies will elucidate whether RNA oxidation plays a role in the pathogenesis of AD. [unreadable] [unreadable]